Need some help with high torque 408 build

I run an xe272hl it idles at 600 pulls to 6000 all day long I run a Holley 850 dp on a single plane m1 . Cam is plenty mild brutal torque your cam is too small & 600 carb will run out of air around 4000 your talking less than a 340 cam which isn't much . A 404/416 needs lots of air bigger cam helps make up for heads